This invention relates to a combined differential gear device in which a planetary gear mechanism and a differential gear mechanism are built in a housing.
In general, a combined differential gear device comprises a housing which is driven for rotation about a rotation axis, and a planetary gear mechanism and a differential gear mechanism which are disposed within the housing. A receiving hole extending in parallel with the rotation axis is formed in the housing. A planetary gear is rotatably (about its own axis) received in this receiving hole. An inner gear and a sun gear are rotatably disposed within the housing with their axes aligned with the rotation axis. The inner gear and the sun gear are in meshing engagement with the planetary gear. The planetary gear mechanism is constituted by the inner gear, the planetary gear and the sun gear.
On the other hand, the differential gear mechanism is arranged within the sun gear. That is, the sun gear has a hollow interior and also serves as a casing of the differential gear mechanism. A pinion gear whose axis is orthogonal to the rotation axis, and a pair of side gears whose axes are aligned with the rotation axis, are disposed within the sun gear such that they are rotatable about their axes. The pinion gear is in meshing engagement with the pair of side gears. The differential gear mechanism is constituted by the pinion gear and the pair of side gears.
In the conventional combined differential gear device, since the planetary gear device and the differential gear device are arranged, side by side, in the radial direction of the housing, the entire device is enlarged in outside diameter. That is, in the conventional combined differential gear device, since the differential gear mechanism is disposed within the sun gear, the sun gear is enlarged in outside diameter. Then, the differential gear mechanism containing the sun gear is enlarged in outside diameter. As a result, the housing is inevitably enlarged in outside diameter. This makes the entire combined differential gear device large in size.
The present invention has been made in order to solve the above problems and its features reside in a combined differential gear device in which a planetary gear mechanism and a differential gear mechanism are built in a housing which is driven for rotation about a rotation axis, the planetary gear mechanism including at least one planetary gear rotatably received in at least one receiving hole which is formed in the housing in parallel with the rotation axis, and an inner gear and a sun gear which are rotatably arranged on the housing with axes thereof aligned with the rotation axis and which are in meshing engagement with the planetary gear, the differential gear mechanism including a casing rotatably disposed within the housing with an axis thereof aligned with the rotation axis and connected to one of the inner gear and the sun gear in such a manner as to rotate in unison therewith, at least one pinion gear rotatably arranged within the casing with an axis thereof orthogonal to the rotation axis, and a pair of side gears arranged within the casing with axes thereof aligned with the rotation axis and being in meshing engagement with the pinion gear, and the planetary gear mechanism and the differential gear mechanism being arranged in adjacent relation in a direction of the rotation axis.
In the above-mentioned construction, it is preferred that the casing includes a connection portion non-rotatably connected to one of the inner gear and the sun gear and a support portion connected to one end portion of the connection portion in a direction of the rotation axis and having a receiving space formed therein, the support portion is disposed away, in a direction of the rotation axis, from one of the inner gear and the sun gear to which the connection portion is connected, and the pinion and the pair of side gears constituting the differential gear mechanism are received in the receiving space.
It is also preferred that an output gear having an outer gear portion connected to the other of the inner gear and the sun gear in such a manner as to rotate in unison therewith is provided at an outer peripheral portion of the housing, and the outer gear portion is arranged at an intermediate portion of the outer peripheral surface of the housing in a direction of the rotation axis.